The present invention relates to an organic-inorganic composite material which is useful as a plastic material of various kinds, a resin additive and a coating material, and to a process for preparing the same.
The conventional material such as metal, glass, wood, paper and the like, has recently been taken over a plastic material due to its molding ability, convenient productivity, lightness in weight, flexibility, excellent mechanical property, excellent electric property and the like. A plastic material is now widely applied to the architecture resources, mechanical parts, or structural parts of electric, or electronic goods, exterior parts or interior parts of an automobile, a vehicle, an aircraft, or a watercraft, and the like. A plastic material is employed for various purposes as such, and various types are available on the market.
A plastic material has been required for cost saving and performance improvement by the market, and the trial for investigation of an alloy of plural kinds of plastics, or a composite of plastics with the other materials, is widely conducted. For example, an organic-inorganic composite material has been investigated in order to improve mechanical performance, heat resistance, and dimensional stability of a plastic material. The organic-inorganic composite material is usually prepared by blending an inorganic material such as glass fiber, and carbon fiber with a plastic material. Mechanical strength, thermal toughness, and dimensional strength of a plastic material seem to be improved by incorporating an inorganic material in short period.
However, compatibility of a plastic material with an inorganic material is generally poor, and it is difficult to make the inorganic material to disperse finely in the plastic material. Thus, the particle size of the inorganic material dispersed in the plastic material is generally not less than the order of micrometer. The particle size exerts a strong influence on strength of the composite material, and the larger the particle size, the weaker the strength (Dynamic Property of Polymer and Composite Material, L. E. Nielsen, Page 253).
Therefore, there have been the limitation due to the particle size, in the case when strength of the conventional organic-inorganic composite material is intended to improve. In addition, microscopic interface strength between the plastic material and the inorganic material may become poor depending on the kind of the plastic material which is employed (e.g., ABS resin, polyamide 6-6, polycarbonate, polyacetal, full aromatic polyester, and the like), and the problems such as lowering of impact strength are raised.
On the other hand, investigation has been made for introducing inorganic element such as Si, Ti, Zr directly in a backbone of the plastic material to prepare an organic-inorganic hybrid polymer material, in order to improve surface hardness, gloss, soil resistance, hardness, heat resistance, weather resistance, and chemical resistance.
The particle size of dispersoid which is present in the organic-inorganic hybrid polymer material is in the order of submicron to not more than nanometer, and dispersoid per molecular unit is also possible. A process for preparing the organic-inorganic hybrid polymer material which is known to those skilled in the art is that an organic monomer or an organic polymer, and an inorganic frame containing compound such as alkylsiloxane are radically copolymerized, or that an inorganic functional group such as alkoxy silane is added to an organic polymer as a pendent group, and the organic polymer is then crosslinked.
Japanese Patent Kokai Publication No. 43679/1993, and 86188/1993 describe a process for preparing an organic-inorganic hybrid polymer material in which a vinyl polymer and a silicone compound having a silane group (Sixe2x80x94H group) are subjected to the hydrosilylation reaction, and then the resultant are crosslinked by the sol-gel method.
Japanese Patent Kokai Publication No. 104710/1996, and 104711/1996 describe the process for preparing an organic-inorganic hybrid polymer material in which a vinyl monomer is radically polymerized using an alkoxysilyl end capped azoic initiator, and the resulting alkoxysilyl end capped vinyl polymer is hydrolyzed and polycondensed.
There is described here polystyrene, polyvinyl chloride, an acrylic resin as the vinyl polymer. The vinyl polymers however are poor in heat resistance and mechanical strength, and are not suitable for employing as a high-performance plastic material, particularly as a structural material and a hard coating material.
Macromolecules, vol. 25, page 4309, 1992, discloses the process for preparing an organic-inorganic hybrid polymer material in which an alkoxysilyl group is linked to a main chain of a polyalkylene oxide polymer, and the resultant is hydrolyzed and polycondensed. As the main chain of the organic-inorganic composite material, Macromol. Chem. Macromol. Symp., vol. 42/43, page 303, 1991, discloses a polyoxazoline polymer, J. Inorg. Organomet. Polym., vol. 5, page 4, 1995, discloses a polyamine polymer, and J. Appl. Polym. Sci., vol. 58, page 1263, 1995, discloses a cellulose polymer.
However, the polymers described above as the main chain of the organic-inorganic composite material, are all hydrophilic. The hydrophilic polymers are hygroscopic, poor in water resistance, and are not suitable for employing as a plastic molded material, a sealing material, a coating raw material, a structural material, a hard coating material, and the like.
We have made a study and succeeded to investigate an organic-inorganic hybrid polymer material made of the engineering plastics which is excellent in heat resistance, mechanical strength, and water resistance, and involves a wide application range for industrial use (Japanese Patent Kokai Publication No. 209596/1999, and 255883/1999). This organic-inorganic hybrid polymer material actually shows, on the performance test, higher heat resistance, surface hardness, mechanical strength, and the like than the conventional engineering plastics, and it is confirmed as very useful material.
The organic-inorganic hybrid polymer material shows improved performance over the commercially available polymer material. However, the rather high cost is required for preparing the organic-inorganic hybrid material, and it involves a problem of impractical for use in general purpose.
According to the present invention, there is provided an organic-inorganic composite material which shows high mechanical strength and high water resistance, requires low cost for preparation, and is preferred to be used as a high performance and a high functional plastic material. The present invention also provides a simple and practical process for preparing the same.
The present invention provides an organic-inorganic composite material which comprises a matrix of an organic polymer (E), metal oxide particles (C) dispersed uniformly in the organic polymer (E), and a surface modifier for allowing the metal oxide particles (C) to disperse uniformly in the organic polymer (E), wherein the surface modifier is another organic polymer (A) which has a functional group formable of a covalent bond to a surface of the metal oxide particles (C).
The organic-inorganic hybrid material of the present invention preferably be prepared by the process comprising the steps of:
(1) obtaining metal oxide particles coated with an organic polymer (A), in which the functional group of the organic polymer (A) is bonded covalently to a surface of the metal oxide particles;
(2) dispersing the metal oxide particles coated with the first organic polymer (A) finely and uniformly in another organic polymer (E); and
(3) setting the resulting mixture.